Explore the significance and implications of soil$-$structure interaction in the design and analysis of civil engineering structures. Discuss the factors influencing the behavior of soil and how they affect the stability and performance of structures built on or within it$.$ Consider the variability of soil properties, including cohesion, friction angle, and compressibility, and how these characteristics are accounted for in geotechnical engineering. Evaluate the role of soil testing methods and the interpretation of results in predicting settlement, bearing capacity, and potential for soil liquefaction. Analyze how advanced modeling techniques and simulation tools are utilized to enhance the accuracy of predictions in complex soil$-$structure systems, and debate the challenges and limitations faced by engineers in this field.